Abstract : Habituation has been defined as a response decrement produced by repeated or continuous stimulation (Harris 1943). Cain and Carlson (1971) have demonstrated that a response induced by electrical brain stimulation (EBS) can habituate. Carlton (1963) suggested that the physiological basis of habituation was accumulation of acetylcholine at central cholenergic synapses and that the effects of this accumulation could be blocked by anticholenergic drugs such as scopolamine. The present experiment was designed to test Carlton's hypothesis by determining the effect of scopolamine upon habituation of EBS-induced running. (Author)